Paper structures, such as toilet tissue, paper towels, and facial tissue, are widely used throughout the home and industry. Many attempts have been made to make such tissue products more consumer preferred. One approach to providing consumer preferred tissue products having bulk and flexibility is illustrated in U.S. Pat. No. 3,994,771 issued Nov. 30, 1976 to Morgan et al. Improved bulk and flexibility may also be provided through bilaterally staggered compressed and uncompressed zones, as shown in U.S. Pat. No. 4,191,609 issued Mar. 4, 1980 to Trokhan.
Another approach to making tissue products more consumer preferred is to dry the paper structure to impart greater bulk, tensile strength, and burst strength to the tissue products. Examples of paper structures made in this manner are illustrated in U.S. Pat. No. 4,637,859 issued Jan. 20, 1987 to Trokhan. Alternatively, a paper structure can be made stronger, without utilizing more cellulosic fibers, by having regions of differing basis weights as illustrated in U.S. Pat. No. 4,514,345 issued Apr. 30, 1985 to Johnson, et. al. Papermaking belts having a semicontinuous pattern and paper made on such belts are disclosed in PCT Publication WO 94/04750 published Mar. 3, 1994 in the name of Ayers et al., and having a U.S. priority date of Aug. 26, 1992. Papermaking belts made using a deformable casting surface process are disclosed in U.S. Pat. No. 5,275,700 issued Jan. 4, 1994 to Trokhan.
Tissue paper manufacturers have also attempted to make tissue products more appealing to consumers by improving the aesthetic appearance of the product. For example, embossed patterns formed in tissue paper products after the tissue paper products have been dried are common. One embossed pattern which appears in cellulosic paper towel products marketed by the Procter and Gamble Company is illustrated in U.S. Pat. No. Des. 239,137 issued Mar. 9, 1976 to Appleman. Embossing methods and/or embossed products are also disclosed in U.S. Pat. No. 3,556,907 issued Jan. 19, 1971 to Nystrand; U.S. Pat. No. 3,867,225 issued Feb. 18, 1975 to Nystrand; and U.S. Pat. No. 3,414,459 issued Dec. 3, 1968 to Wells.
However, embossing a dry paper web typically imparts a particular aesthetic appearance to the paper structure at the expense of other properties of the structure. In particular, embossing disrupts bonds between fibers in the cellulosic structure. This disruption occurs because the bonds are formed and set upon drying of the embryonic fibrous slurry. After drying the paper structure, moving fibers normal to the plane of the paper structure by embossing breaks fiber to fiber bonds. Breaking bonds results in reduced tensile strength of the dried paper web. In addition, embossing is typically done after creping of the dried paper web from the drying drum. Embossing after creping can disrupt the creping pattern imparted to the web. For instance, embossing can eliminate the creping pattern in some portions of the web by compacting the creping pattern. Such a result is undesirable because the creping pattern improves the softness and flexibility of the dried web.
In addition, dry embossing a paper structure acts to stretch or draw the paper structure around the perimeter of the embossments. As a result, the paper structure around the perimeter of the embossments will have a reduced thickness relative to the non-embossed portion of the paper web.
U.S. patent application Ser. No. 07/718,452, Tissue Paper Having Large Scale, Aesthetically Discernible Patterns and Apparatus for Making Same, filed Jun. 19, 1991 to be issued as U.S. Pat. No. 5,328,565 on Jul. 12, 1994 in the name of Rasch et al. discloses a single lamina paper structure having at least three visually discernible regions. Rasch et al. teaches the three regions are visually distinguishable by an optically intensive property such as crepe frequency, elevation, or opacity. While the structures of Rasch et al. provide an improvement over embossed paper structures, there is a need to provide tissue products having improved visually discernible patterns over those taught in Rasch et al. Therefore, those involved in the papermaking field continue to search for ways to make paper structures having highly discernible aesthetic patterns without sacrificing desirable paper web properties.
Accordingly, one object of the present invention is to provide a paper structure having visually discernible patterns without the need for embossing a dried paper web.
Another object of the present invention is to provide a paper structure having visually discernible patterns without sacrificing desirable paper web properties such as tensile strength and sheet flexibility.
Another object of the present invention is to provide a paper structure having a first region disposed at a first elevation and having a first thickness, a second region disposed at a second elevation different from the first elevation and having a second thickness, a third region disposed at a third region and having a third thickness greater than the first thickness, and a fourth transition region interconnecting the second region with at least one of the first and third regions, the transition region having a fourth thickness greater than the second thickness and greater than or equal to the first thickness.
Another object of the present invention is to provide an apparatus and method for forming the paper structure of the present invention.
Another object of the present invention is provide a paper structure characterized in having enhanced bulk caliper and roll compressibility.